The present invention relates to a device for the production of compressed gas, where compressing action is discontinued when the receiving-end pressure has reached a predetermined level. Such a device is known from DE-AS 1 061 475.
The known device for the production of compressed gas has a connection between a compression chamber and a suction chamber of the compressor. This connection discontinues air feeding to a receiving end when a predetermined pressure has been reached or exceeded on the receiving end. The compressor is then in the idling phase, where air is sucked from the suction chamber, or from the suction side, towards the compression chamber and is expelled again along the same path in the reverse direction. No air can now be conveyed through a compression regulating valve subjected to the receiving-end pressure.
When the pressure on the receiving end increases to a predetermined level, an idling valve is actuated to connect the compression chamber to the suction chamber. The idling valve is actuated by the compression regulating valve located between the outlet of the compressor and the receiving end.
When the internal cross-section of the pressure pipe going to the receiving end is reduced, e.g., through the deposit of oil or carbon, excessive dynamic pressure builds up in the compression chamber of the compressor. The increased pressure may cause an undesirable heating of the compressor.
The reduction in the cross-section of the pressure pipe progresses only at a slow pace. The compression regulating valve of the known device cannot recognize the cross-section reduction, since this valve only measures the pressure on the receiving-end. Therefore, the pressure in the compression chamber could rise to an unacceptably high value before the pressure at the receiving-end reaches the same level. Since the pressure is only measured at the receiving-end, the idling valve cannot be switched over at the proper time to connect the compression chamber to the suction chamber. Therefore, the compressing action is not discontinued at the proper time.